<html>
<head>
	<meta charset="UTF-8">
	<meta content="IE=edge" http-equiv="X-UA-Compatible">
	<meta content="initial-scale=1.0, maximum-scale=1.0, user-scalable=no, width=device-width" name="viewport">
	<title>2428：[HAOI2006]均分数据</title>
	<!-- css -->
	<link href="../css/base.min.css" rel="stylesheet">
	<link href="../css/project.min.css" rel="stylesheet">
	
	<!-- favicon -->
	<!-- ... -->
</head>
<body class="page-brand">
	<header class="header header-transparent header-waterfall ui-header">
		<ul class="nav nav-list pull-left">
			<li>
				<a data-toggle="menu" href="#menu">
					<span class="icon icon-lg">menu</span>
				</a>
			</li>
		</ul>
		<a class="header-logo header-affix-hide margin-left-no margin-right-no" data-offset-top="213" data-spy="affix">[HAOI2006]均分数据</a>
		<span class="header-logo header-affix margin-left-no margin-right-no" data-offset-top="213" data-spy="affix">[HAOI2006]均分数据</span>
	</header>
	<nav aria-hidden="true" class="menu" id="menu" tabindex="-1">
		<div class="menu-scroll">
			<div class="menu-content">
				<a class="menu-logo" href="../index.html">BZOJ离线题库</a>
				<ul class="nav">
					<li>
						<a class="waves-attach" data-toggle="collapse" href="#problems">题目</a>
						<ul class="menu-collapse collapse in" id="problems">
							<li>
								<a class="waves-attach" href="../index.html">主页</a>
							</li>
							<li>
								<a class="waves-attach" href="../list.html">题目列表</a>
							</li>
						</ul>
					</li>
					<li>
						<a class="collapsed waves-attach" data-toggle="collapse" href="#about">关于</a>
						<ul class="menu-collapse collapse" id="about">
							<li>
								<a class="waves-attach" href="../about.html">关于此项目</a>
							</li>
						</ul>
					</li>
					
				</ul>
			</div>
		</div>
	</nav>
	<main class="content">
		<div class="content-header ui-content-header">
			<div class="container">
				<h1 class="content-heading">
                [HAOI2006]均分数据                </h1>
                <p>时间限制：5s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：128MB</p>			</div>
		</div>
		<div class="container">
			<section class="content-inner margin-top-no">
				<div class="row">
					<div class="col-lg-13 col-md-13">
						<div class="card margin-bottom-no">
							<div class="card-main">
								<div class="card-inner">
									
                                <h3>题目描述</h3><p><p><span style="line-height: 150%; text-indent: 21pt; font-family: 宋体;">已知</span><span lang="EN-US" style="line-height: 150%; text-indent: 21pt;">N</span><span style="line-height: 150%; text-indent: 21pt; font-family: 宋体;">个正整数：</span><span lang="EN-US" style="line-height: 150%; text-indent: 21pt;">A1</span><span style="line-height: 150%; text-indent: 21pt; font-family: 宋体;">、</span><span lang="EN-US" style="line-height: 150%; text-indent: 21pt;">A2</span><span style="line-height: 150%; text-indent: 21pt; font-family: 宋体;">、&hellip;&hellip;、</span><span lang="EN-US" style="line-height: 150%; text-indent: 21pt;">An </span><span style="line-height: 150%; text-indent: 21pt; font-family: 宋体;">。今要将它们分成</span><span lang="EN-US" style="line-height: 150%; text-indent: 21pt;">M</span><span style="line-height: 150%; text-indent: 21pt; font-family: 宋体;">组，使得各组数据的数值和最平均，即各组的均方差最小。均方差公式如下：</span></p>
<p><img src="../file/2428_0.jpg" width="390" height="94" alt="" />,<span style="font-family:宋体;mso-ascii-font-family:&quot;Times New Roman&quot;;
mso-hansi-font-family:&quot;Times New Roman&quot;">其中</span><span style="font-family:
宋体">&sigma;</span><span style="font-family:宋体;mso-ascii-font-family:&quot;Times New Roman&quot;;
mso-hansi-font-family:&quot;Times New Roman&quot;">为均方差，<img src="../file/2428_1.jpg" width="34" height="46" alt="" /></span><span style="font-family:宋体;mso-ascii-font-family:
&quot;Times New Roman&quot;;mso-hansi-font-family:&quot;Times New Roman&quot;">是各组数据和的平均值，</span><span lang="EN-US">x<sub>i</sub></span><span style="font-family:宋体;mso-ascii-font-family:
&quot;Times New Roman&quot;;mso-hansi-font-family:&quot;Times New Roman&quot;">为第</span><span lang="EN-US">i</span><span style="font-family:宋体;mso-ascii-font-family:&quot;Times New Roman&quot;;
mso-hansi-font-family:&quot;Times New Roman&quot;">组数据的数值和。</span></p>
<p class="MsoNormal"><span lang="EN-US">&nbsp;</span></p>
<p></p></p><hr/><h3>输入格式</h3><p><div>第一行是两个整数，表示N,M的值（N是整数个数，M是要分成的组数）</div>
<div>第二行有N个整数，表示A1、A2、&hellip;&hellip;、An。整数的范围是1--50。</div>
<div>（同一行的整数间用空格分开）</div></p><hr/><h3>输出格式</h3><p><p><a id="fck_paste_padding"><span style="font-family:宋体;
mso-ascii-font-family:&quot;Times New Roman&quot;;mso-hansi-font-family:&quot;Times New Roman&quot;">这一行只包含一个数，表示最小均方差的值</span><span lang="EN-US">(</span><span style="font-family:宋体;mso-ascii-font-family:&quot;Times New Roman&quot;;
mso-hansi-font-family:&quot;Times New Roman&quot;">保留小数点后两位数字</span><span lang="EN-US">)</span><span style="font-family:宋体;mso-ascii-font-family:&quot;Times New Roman&quot;;mso-hansi-font-family:
&quot;Times New Roman&quot;">。</span></a></p>
<p></p>
<p></p>
<p></p>
<p></p></p><hr/><h3>样例输入</h3><pre> 6  3
1  2  3  4  5  6</pre><hr/><h3>样例输出</h3><pre>0.00</pre><hr/><h3>提示</h3><p><p>对于全部的数据，保证有K&lt;=N &lt;= 20，2&lt;=K&lt;=6</p></p><hr/><h3>题目来源</h3><p>Day2</p>
								</div>
							</div>
						</div>
					</div>
				</div>
				
				
			</section>
		</div>
	</main>

	<div class="fbtn-container">
		<div class="fbtn-inner">
			<a class="fbtn fbtn-lg fbtn-brand-accent waves-attach waves-circle waves-light waves-effect" data-toggle="dropdown" aria-expanded="true"><span class="fbtn-text fbtn-text-left">Menu</span><span class="fbtn-ori icon">apps</span><span class="fbtn-sub icon">close</span></a>
			<div class="fbtn-dropup">
				<a class="fbtn fbtn-brand waves-attach waves-circle waves-light waves-effect" href="../list.html" target="_self"><span class="fbtn-text fbtn-text-left">题目列表</span><span class="icon">menu</span></a>
				<a class="fbtn fbtn-green waves-attach waves-circle waves-effect" href="../index.html" target="_self"><span class="fbtn-text fbtn-text-left">返回主页</span><span class="icon">home</span></a>
				<a class="fbtn waves-attach waves-circle waves-effect" href="http://www.lydsy.com/JudgeOnline/submitpage.php?id=2428" target="_blank"><span class="fbtn-text fbtn-text-left">提交代码</span><span class="icon">send</span></a>
				<a class="fbtn fbtn-orange waves-attach waves-circle waves-effect" href="http://www.lydsy.com/JudgeOnline/wttl/wttl.php?pid=2428" target="_blank"><span class="fbtn-text fbtn-text-left">试题讨论</span><span class="icon">chat</span></a>
				
			</div>
		</div>
	</div>

	<!-- js -->
	<script src="../js/jquery.min.js"></script>
	<script src="../js/base.min.js"></script>
	<script src="../js/project.min.js"></script>
</body>
</html>